This invention relates to a blood vessel piercing instrument used to introduce into the blood vessel a guide wire for guiding a catheter to a target region in the blood vessel.
Various guide wires and blood vessel piercing instruments for introducing a guide wire into the blood vessel are used. Conventional blood vessel piercing instruments generally comprise an outer tube assembly consisting of an outer tube for introducing a guide wire into the blood vessel and an outer tube hub attached to the rear end portion of the outer tube and an inner needle assembly consisting of an inner needle which is extractably inserted in the outer tube assembly and has a piercing edged surface formed at the front end and an inner needle hub which is attached to the rear end portion of the inner needle and engages with the rear end of the outer tube hub.
In a typical conventional blood vessel piercing instrument 50, the metal inner needle 51 protrudes from the front end of the metal outer tube 52 as shown in FIG. 11, and the outer tube 52 is thrust into the blood vessel along with the inner needle.
In such a conventional blood vessel piercing instrument 50, a step h is formed between the outside surface of the metal inner needle 51 and the front end of the metal outer tube 52. This step often causes a pain to the patients when the instrument is thrust into the blood vessel. However, it is difficult to employ a structure in which the inside surface of the front end of the outer tube comes in close contact with the outside surface of the inner needle in order to eliminate the step because the outer tube is made of a metal. If this structure is used for the metal outer tube which does not expand and has a high frictional resistance, removal of the inner needle will be difficult.
Further, the hard front end of the metal outer tube can cause a damage to the wall of the blood vessel while the outer tube is left inserted in the blood vessel until the outer tube is removed after a guide wire is inserted into the blood vessel. Sometimes, the insertion of a guide wire is difficult or causes a pain to the patient because of an insufficient elasticity of the metal outer tube.
Some conventional blood vessel piercing instruments have the outer tube made of a synthetic resin. The resin outer tube of those conventional blood vessels, however, has not a sufficient strength and can bend in angles or collapse after the inner needle is removed.